Poxviral oncolytic vectors

ABSTRACT

The present invention relates to a poxvirus comprising a defective F4L and/or I4L gene, to composition comprising such poxvirus and to the methods and use of such compositions and poxviruses for therapeutic purposes, and more particularly for the treatment of cancer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-part Application of U.S. patentapplication Ser. No. 12/743,407, filed on Oct. 21, 2010, which is a U.S.National Stage of PCT/EP2008/009720, filed on Nov. 17, 2008, whichdesignated the United States and was published in the English languageon May 28, 2009, as WO 2009/065546 A1 and claims priority under 35U.S.C. §119 to EP 07301557.0, filed on Nov. 19, 2007; the content ofeach is hereby expressly incorporated by reference in their entiretiesfor all purposes and each is assigned to the assignee hereof.

TECHNICAL FIELD

Oncolytic viruses are a class of novel therapeutic agents used for thetreatment of cancer that have the unique property of tumor-dependentself-perpetuation (HERMISTON. A demand for next-generation oncolyticadenoviruses. Current opinion in molecular therapeutics. 2006, vol. 8,no. 4, p. 322-30.). Oncolytic viruses are capable of selectivereplication in malignant cells and therefore offer levels of potency andspecificity that are potentially far higher than conventional treatmentsfor cancer (FISHER. Striking out at disseminated metastases: thesystemic delivery of oncolytic viruses. Current opinion in moleculartherapeutics. 2006, vol. 8, no. 4, p. 301-13.). The benefit of usingthese viruses is that as they replicate, they lyse their host cells.Cancer cells are ideal hosts for many viruses because they have theantiviral interferon pathway inactivated or have mutated tumoursuppressor genes that enable viral replication to proceed unhindered(CHERNAJOVSKY, et al. Fighting cancer with oncolytic viruses. Britishmedical journal. 2006, vol. 332, no. 7534, p. 170-2.).

Some viruses are naturally able to selectively replicate in tumoralcells but oncolytic viruses can also be obtained by modifying naturallyoccurring viruses. For this purpose, the main strategies used currentlyto modify the viruses include: functional deletions in essential viralgenes; tumor- or tissue-specific promoters used to control theexpression of these viral genes; and tropism modification to redirectadenovirus to the cancer cell surface. In the near future, oncolyticadenoviruses need to be optimized to fully realize their potential ascritical anticancer tools and, thus, improve the prognosis for patientswith malignant gliomas (JIANG, et al. Oncolytic adenoviruses asantiglioma agents. Expert review of anticancer therapy. 2006, vol. 6,no. 5, p. 697-708.).

For example, ONYX-015, an adenovirus modified selectively to replicatein and kill cells that harbor p53 mutations, is under development byOnyx Pharmaceuticals for the potential treatment of various solidtumors, including head and neck, gastrointestinal and pancreatic tumors.It is a recombinant adenovirus that carries a loss-of-function mutationat the E1B locus, the product of which is a 55 kDa protein that binds toand inactivates the p53 tumor suppressor protein. Thus, the ONYX-015adenovirus is supposed to leave normal cells unaffected. Mutations inthe p53 tumor suppressor gene are the most common type of geneticabnormality in cancer, occurring in more than half of all major cancertypes. Thus, these cells are susceptible to the virus, which willreadily replicate and cause cell death. ONYX-015 is in ongoing phase IIItrials for the treatment of recurrent head and neck cancer, phase IItrials for colorectal, ovary, pancreas and mouth tumors, and phase Itrials for digestive disease, esophagus and liver tumors (COHEN, et al.ONYX-015. Onyx Pharmaceuticals. Current opinion in investigationaldrugs. 2001, vol. 2, no. 12, p. 1770-5.).

Naturally oncolytic viruses are replication-competent viruses that havean innate ability to selectively infect and kill tumor cells. Despitebeing used in the original attempts to treat cancer with live virusesfive decades ago, interest in naturally oncolytic viruses has laggedbehind the support for engineered adenoviruses and herpesviruses ascancer therapeutics. Recently, however, there has been renewed interestin the high potency and selectivity of these naturally occurring agents(ROBERTS, et al. Naturally oncolytic viruses. Current opinion inmolecular therapeutics. 2006, vol. 8, no. 4, p. 314-21.).

Among naturally oncolytic viruses, Vaccinia viruses (a Poxyiridae)possess many of the key attributes necessary for an ideal viral backbonefor use in oncolytic virotherapy. These include a short lifecycle, withrapid cell-to-cell spread. strong lytic ability, a large cloningcapacity and well-defined molecular biology. In addition, althoughcapable of replicating in human cells, they are not considered a naturalhealth problem and are especially well characterized having beendelivered to millions of individuals during the campaign to eradicatesmallpox. Early clinical results using either vaccine strains orgenetically modified vaccinia strains have demonstrated antitumoreffects (THORNE, et al. Vaccinia virus and oncolytic virotherapy ofcancer. Current opinion in molecular therapeutics. 2005, vol. 7, no. 4,p. 359-65.).

In contrast, the poxvirus myxoma virus is a novel oncolytic candidatethat has no history of use in humans directly, as it has a distinct andabsolute host species tropism to lagomorphs (rabbits). Myxoma virus hasbeen recently shown to be able to also selectively infect and kill humantumor cells, a unique tropism that is linked to dysregulatedintracellular signalling pathways found in the majority of humancancers. This review outlines the existing knowledge on the tropism ofmyxoma virus for human cancer cells, as well as preclinical dataexhibiting its ability to infect and clear tumors in animal models ofcancer (STANFORD, et al. Myxoma virus and oncolytic virotherapy: a newbiologic weapon in the war against cancer. Expert opinion on biologicaltherapy. 2007, vol. 7, no. 9, p. 1415-25.).

TECHNICAL PROBLEM

The injection of high doses of Poxviruses necessary to achieve anantitumoral effect raised toxicity issues. The majority of adverseevents are minor, adverse reactions that are usually linked to Vacciniavirus are self-limited and include fever, headache, fatigue, myalgia,chills, local skin reactions, nonspecific rashes, erythema multiforme,lymphadenopathy, and pain at the vaccination site. Other reactions mightrequire additional therapies (e.g., VIG, a first-line therapy andcidofovir, a second-line therapy). Adverse reactions that might requirefurther evaluation or therapy include inadvertent inoculation,generalized vaccinia (GV), eczema vaccinatum (EV), progressive vaccinia(PV), postvaccinial central nervous system disease, and fetal vaccinia(CONO, et al. Smallpox vaccination and adverse reactions. Guidance forclinicians. MMWR. Recommendations and reports Morbidity and mortalityweekly report. Recommendations and reports/Centers for Disease Control.2003, vol. 52, no. RR-4, p. 1-28.).

Thus, there is need for safer Poxviruses with an oncolytic activity asgood as to their natural counterparts.

BACKGROUND ART

U.S. Pat. No. 5,364,773 (VIROGENETICS CORPORATION (TROY, N.Y.)) 15 Nov.1994 describes a modified recombinant poxvirus, more particularly avaccinia virus having inactivated nonessential virus-encoded encodedgenetic functions so that the recombinant poxvirus has attenuatedvirulence and enhanced safety. In particular, the genetic functions areinactivated by deleting an open reading frame encoding a virulencefactor or by insertional inactivation of an open reading frame encodinga virulence factor. More particularly, this patent describes a vacciniavirus in which the open reading frame of for J2R, B13R+B14R, A26L, A56R,C7L-K1L, and I4L has been inactivated. This virus (NYVAC) can beengineered as a vector for a foreign nucleic acid and used as a vaccinefor inducing an immunological response in a host animal. However, N YVACis unable to efficiently replicate in most mammalian cells and can notbe used as an oncolytic virus (XIANGZHI, et al. Vaccinia virus K1Lprotein supports viral replication in human and rabbit cells through acell-type-specific set of its ankyrin repeat residues that are distinctfrom its binding site for ACAP2. Journal of virology. 2006, vol. 353,no. 1, p. 220-233.).

WO 2004/014314 (KIRN DAVID (US)) 19 Feb. 2004 describes an alteredvaccinia virus that comprises one or more mutations in its viral genome.Described mutations are in one or more of the following classes ofpolypeptides: 1) interferon-modulating polypeptide; 2) complementcontrol polypeptide; 3) TNF or chemokine-modulating polypeptide; 4)serine protease inhibitor; 5) IL-Ip modulating polypeptide; 6)non-infectious EEV form polypeptides; and, 7) viral polypeptide that actto inhibit release of infectious virus from cells (anti-infectious virusform polypeptide). In addition, mutations in A41L or C11R of vacciniavirus are also disclosed.

Vaccinia genome regions such as A34R, A41L, A53R, B5R, B7R, B8R, B13R,B15R, B18R, B22R, B28R, B29R, CUR, E3L, K2L, N1L, vC12L, and vCKBP aremore particularly described in this application. Methods of theinvention involve using any of the poxviruses discussed herein. Theinventors also disclose methods to treat cancer by administering to thecancer cell or patient an effective amount of this altered vacciniavirus.

DISCLOSURE OF INVENTION

The inventors have surprisingly discovered that poxviruses comprising adefective I4L and/or F4L gene have an improved safety profile but keptan equivalent oncolytic activity (compared to their naturalcounterpart).

The present invention relates to a poxvirus comprising a defective I4Land/or F4I gene with the proviso that said poxvirus is not NYVAC.

As used throughout the entire application, the terms “a” and “an” areused in the sense that they mean “at least one”, “at least a first”,“one or more” or “a plurality” of the referenced components or steps,unless the context clearly dictates otherwise. For example, the term “acell” includes a plurality of cells, including mixtures thereof.

The term “and/or” wherever used herein includes the meaning of “and”,“or” and “all or any other combination of the elements connected by saidterm”.

The term “about” or “approximately” as used herein means within 20%,preferably within 10%, and more preferably within 5% of a given value orrange.

As used herein, the terms “comprising” and “comprise” are intended tomean that the products, compositions and methods include the referencedcomponents or steps, but not excluding others. “Consisting essentiallyof” when used to define products, compositions and methods, shall meanexcluding other components or steps of any essential significance. Thus,a composition consisting essentially of the recited components would notexclude trace contaminants and pharmaceutically acceptable carriers.“Consisting of” shall mean excluding more than trace elements of othercomponents or steps.

As used herein, the term “poxvirus comprising a defective gene” refersto a poxvirus comprising a deletion, substitution or addition in one ormore nucleic acid of the defective gene, or any combination of thesepossibilities wherein said modifications lead to the inability for thevirus to produce a protein having the activity of the protein producedby the unmodified gene. In a preferred embodiment of the invention, apoxvirus comprising a defective gene refers to a poxvirus in which thewhole gene sequence has been deleted. Mutation can be made in a numberof ways known to those skilled in the art using recombinant techniques.Methods for modifying the genome of a poxvirus are available in the art.For example the methods disclosed in MCCART, et al. Systemic cancertherapy with a tumor selective vaccinia virus mutant lacking thymidinekinase and vaccinia growth factor genes. Cancer res. 2001, no. 61, p.8751-57., KIM, et al. Systemic armed oncolytic ans immunologic therapyfor cancer with JX-594, a targeted poxvirus expressing GM-CSF. MolecularTherapeutic. 2006, no. 14, p. 361-70., WO 2004/014314 (KIRN DAVID (US))19 Feb. 2004 and U.S. Pat. No. 5,364,773 (VIROGENETICS CORPORATION(TROY, N.Y.)) 15 Nov. 1994 can be used to produce the poxvirus of theinvention. The methods disclosed in the example of the presentapplication are particularly relevant to produce a poxvirus according tothe invention. Sequences of the genome of various poxviruses areavailable in the art, for example, the vaccinia virus, cowpox virus,Canarypox virus, Ectromelia virus, Myxoma virus genomes are available inGenbank (accession number NC_006998, NC_003663, NC_005309, NC_004105,NC_001132 respectively)

As used herein the term “poxvirus” refers to a virus belonging to thePoxyiridae family. According to a preferred embodiment, the poxvirusaccording to the invention belongs to the Chordopoxyirinae subfamily,more preferably to the Orthopoxvirus genus and even more preferably tothe Vaccinia virus specie.

For example, Vaccinia virus strains Dairen I, IHD-J, L-IPV, LC16M8,LC16MO, Lister, LIVP, Tashkent, WR 65-16, Wyeth, Ankara, Copenhagen,Tian Tan and WR can be used. According to a particularly preferredembodiment, the poxvirus according to the invention is a Vaccinia virusstrains Copenhagen.

The poxvirus vaccinia contains a large duplex DNA genome (187 kilobasepairs) and is a member of the only known family of DNA viruses thatreplicates in the cytoplasm of infected cells. Because the infected cellmust deliver large amounts of DNA precursors to cytoplasmic replicationsites, the virus encodes and expresses many enzymatic activitiesrequired for DNA metabolism and synthesis, including ribonucleotidereductase and deoxyuridine 5′-triphosphate nucleotidohydrolase(dUTPase).

Ribonucleotide reductase (EC 1.17.4.1) catalyzes the reduction ofribonucleotides to deoxyribonucleotides, a reaction that represents thefirst committed step in DNA biosynthesis. The viral enzyme is similar insubunit structure to the mammalian enzyme, being composed of twoheterologous subunits, designed R1 and R2. The genes that encode theviral ribonucleotide reductase subunits have been sequenced andlocalized to positions on the vaccinia genome, separated by 35 kilobases(SLABAUGH, et al. Journal of virology. 1988, vol. 62, p. 519-27.;TENGELSEN, et al. Virology. 1988, no. 164, p. 121-31.; SCHMITT, et al.Journal of virology. 1988, no. 62, p. 1889-97.). The monomers of thevaccinia virus large subunit (designated R1, encoded by the I4L gene)are 86-kDa polypeptides, and contain binding sites for nucleotidesubstrates an allosteric effectors (SLABAUGH, et al. Journal ofvirology. 1984, no. 52, p. 507-14.; SLABAUGH, et al. Journal ofvirology. 1984, no. 52, p. 501-6.). The small subunit (designated R2,encoded by the F4L gene) is a homodimer comprising two 37-kDapolypeptides; each polypeptide contains an iron-stabilized protein-basedfree radical that is required for catalysis (HOWELL, et al. Journal ofBiological Chemistry. 1992, no. 267, p. 1705-11.). Sequences for the I4Land F4L genes and their locations in the genome of various poxvirus areavailable in public databases, for example via accession numberDQ437594, DQ437593, DQ377804, AH015635, AY313847, AY313848, NC_003391,NC_003389, NC_003310, M35027, AY243312, DQ011157, DQ011156, DQ011155,DQ011154, DQ011153, Y16780, X71982, AF438165, U60315, AF410153,AF380138, U86916, L22579, NC_006998, DQ121394 and NC_008291.

The gene nomenclature used herein is that of Copenhagen vaccinia strainand is used also for the homologous genes of other poxyiridae unlessotherwise indicated. However, gene nomenclature may be differentaccording to the pox strain. For information, correspondence betweenCopenhagen and MVA genes can be found in Table I of ANTOINE. Virology.1998, no. 244, p. 365-396.

According to a preferred embodiment, the poxvirus of the inventionfurther comprises a defective J2R gene.

The J2R gene encodes a Thymidine kinase (TK) which form part of thesalvage pathway for pyrimidine deoxyribonucleotide synthesis. Thereaction catalysed by TK involves the transfer of a γ-phosphoryl moietyfrom ATP to 2′ deoxy-thymidine (dThd) to produce thymidine5′-monophosphate (dTMP). Vaccinia virus' TK is of type 2. Type 2 TKshave a smaller polypeptide chain compared to type 1, being of ˜25 KDabut form homotetramers. They are sensitive to the feedback inhibitorsdTDP or dTTP, which are generated at the end of the metabolic pathway.Type 2 TKs have a much narrower substrate specificity compared to type 1TKs and only phosphorylate 2′ deoxyuridine (dU) and/or dThd (EL OMARI,et al. Structure of vaccinia virus thymidine kinase in complex withdTTP: insights for drug design. BMC structural biology. 2006, no. 6, p.22.).

Poxviruses defective for the J2R region and methods to obtain them areavailable in the art. For example, the teaching of MCCART, et al.Systemic cancer therapy with a tumor-selective vaccinia virus mutantlacking thymidine kinase and vaccinia growth factor genes. cancerresearch. 2001, vol. 61, no. 24, p. 8751-7., PUHLMANN, et al. Vacciniaas a vector for tumor-directed gene therapy: biodistribution of athymidine kinase-deleted mutant. Cancer gene therapy. 2000, vol. 7, no.1, p. 66-73., GNANT, et al. Systemic administration of a recombinantvaccinia virus expressing the cytosine deaminase gene and subsequenttreatment with 5-fluorocytosine leads to tumor-specific gene expressionand prolongation of survival in mice. Cancer Research. 1999, vol. 59,no. 14, p. 3396-403. can be used to produced a poxviruses deleted forthe J2R region.

According to a preferred embodiment, the poxvirus of the inventionfurther comprises a defective F2L gene.

Deoxyuridine 5′-triphosphate nucleotidohydrolase (dUTPase, EC 3.6.1.23)catalyzes the hydrolysis of dUTP to dUMP and pyrophosphate in thepresence of Mg(2+) ions. dUTPase, in removing dUTP from the dNTP pooland generating dUMP, is involved in both maintaining the fidelity of DNAreplication and in proviging the precursor for the production of TMP bythymidylate synthase. Vaccinia dUTPase is a 15 kDa protein encoded bythe F2L gene (MCGEOGH. Nucleic Acids Research. 1990, no. 18, p. 4105-10.BROYLES. Virology. 1993, no. 195, p. 863-5.). Sequence of the F2L geneof the vaccinia virus is available in genbank via accession numberM25392, sequences and locations of the F2L gene in various poxvirusesgenomes are also available in genbank, for example, via accession numberNC_006998, DQ121394, NC_001611, AY689436, AY689437, NC_008291, DQ437594,DQ437593, AY313847, AY313848, NC_006966, NC_005309, NC_003391,NC_003389, NC_001132, NC_003310, NC_002188, M35027, AY243312, AF170726,DQ011157, DQ011156, DQ011155, DQ011154, DQ011153, X94355, Y16780,AY318871, U94848, AF198100 and M34368.

According to a preferred embodiment, the poxvirus according to theinvention further comprises a nucleic acid of interest.

In a preferred embodiment, the nucleic acid of interest contains atleast one sequence of interest encoding a gene product which is atherapeutic molecule (i.e. a therapeutic gene). A “therapeutic molecule”is one which has a pharmacological or protective activity whenadministered appropriately to a patient, especially patient sufferingfrom a disease or illness condition or who should be protected againstthis disease or condition. Such a pharmacological or protective activityis one which is expected to be related to a beneficial effect on thecourse or a symptom of said disease or said condition. When the skilledman selects in the course of the present invention a gene encoding atherapeutic molecule, he generally relates his choice to resultspreviously obtained and can reasonably expect, without undue experimentother than practicing the invention as claimed, to obtain suchpharmacological property. According to the invention, the sequence ofinterest can be homologous or heterologous to the target cells intowhich it is introduced. Advantageously said sequence of interest encodesall or part of a polypeptide, especially a therapeutic or prophylacticpolypeptide giving a therapeutic or prophylactic property. A polypeptideis understood to be any translational product of a polynucleotideregardless of size, and whether glycosylated or not, and includespeptides and proteins. Therapeutic polypeptides include as a primaryexample those polypeptides that can compensate for defective ordeficient proteins in an animal or human organism, or those that actthrough toxic effects to limit or remove harmful cells from the body.They can also be immunity conferring polypeptides which act asendogenous antigen to provoke a humoral or cellular response, or both.

Examples of polypeptides encoded by a therapeutic gene include genescoding for a cytokine (alpha, beta or gamma interferon, interleukin, inparticular IL-2, IL-6, IL-10 or IL-12, a tumor necrosis factor (TNF), acolony stimulating factor GM-CSF, C-CSF, M-CSF . . . ), aimmunostimulatory polypeptide (B7.1, B7.2 and the like), a coagulationfactor (FVIII, FIX . . . ), a growth factor (Transforming Growth FactorTGF, Fibroblast Growth Factor FGF and the like), an enzyme (urease,renin, thrombin, metalloproteinase, nitric oxide synthase NOS, SOD,catalase . . . ), an enzyme inhibitor (alpha1-antitrypsin, antithrombinIII, viral protease inhibitor, plasminogen activator inhibitor PAI-1),the CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) protein,insulin, dystrophin, a MHC antigen of class I or II, a polypeptide thatcan modulate/regulate expression of cellular genes, a polypeptidecapable of inhibiting a bacterial, parasitic or viral infection or itsdevelopment (antigenic polypeptides, antigenic epitopes, transdominantvariants inhibiting the action of a native protein by competition . . .), an apoptosis inducer or inhibitor (Bax, Bcl2, BclX . . . ), acytostatic agent (p21, p 16, Rb . . . ), an apolipoprotein (ApoAl,ApoAlV, ApoE . . . ), an inhibitor of angiogenesis (angiostatin,endostatin . . . ), an angiogenic polypeptide (family of VascularEndothelial Growth Factors VEGF, FGF family, CCN family including CTGF,Cyr61 and Nov), an oxygen radical scaveyer, a polypeptide having ananti-tumor effect, an antibody, a toxin, an immunotoxin and a marker(beta-galactosidase, luciferase . . . ) or any other genes of interestthat are recognized in the art as being useful for the treatment orprevention of a clinical condition.

Suitable anti-tumor genes include but are not limited to those encodingtumor suppressor genes (e.g. Rb, p53, DCC, NF-1, Wilm's tumor, NM23,BRUSH-1, p16, p21, p56, p73 as well as their respective mutants),suicide gene products, antibodies, polypeptides inhibiting cellulardivision or transduction signals.

According to a particularly preferred embodiment, the poxvirus of theinvention further comprises a suicide gene.

Suicide gene refers to a gene coding a protein able to convert aprecursor of a drug into a cytoxic compound.

Suicide genes comprise but are not limited to genes coding proteinhaving a cytosine deaminase activity, a thymidine kinase activity, anuracil phosphoribosyl transferase activity, a purine nucleosidephosphorylase activity and/or a thymidylate kinase activity.

Examples of suicide genes and corresponding precursors of a drugcomprising one nucleobase moiety are disclosed in the following table:

TABLE 1 Suicide gene predrug Thymidine Kinase Ganciclovir; Ganciclovirelaidic acid ester; penciclovir; Acyclovir; Valacyclovir;(E)-5-(2-bromovinyl)-2′-deoxyuridine; zidovudine;2′-Exo-methanocarbathymidine Cytosine deaminase 5-Fluorocytosine Suicidegene predrug Purine nucleoside 6-Methylpurine deoxyriboside;phosphorylase Fludarabine uracil phosphoribosyl 5-Fluorocytosine;transferase 5-Fluorouracil thymidylate kinase. Azidothymidine

According to a preferred embodiment of the invention, the suicide genecodes a protein having at least a CDase activity. CDase is involved inthe pyrimidine metabolic pathway by which exogenous cytosine istransformed into uracil by means of a hydrolytic deamination. WhileCDase activities have been demonstrated in prokaryotes and lowereukaryotes (JUND, et al. Journal of Bacteriology. 1970, no. 102, p.607-15.; BECK, et al. Journal of Bacteriology. 1972, no. 110, p.219-28.; HOEPRICH, et al. Journal of Infectious Diseases. 1974, no. 130,p. 112-18.; ESDERS, et al. J. biol. chem. 1985, no. 260, p. 3915-22.),they are not present in mammals (KOECHLIN, et al. Biochemicalpharmacology. 1966, no. 15, p. 435-46.; POLAK, et al. Chemotherapy.1976, no. 22, p. 137-53.).

CDase also deaminates an analogue of cytosine, i.e. 5-fluorocytosine(5-FC), thereby forming 5-fluorouracil (5-FU), which is a compound whichis highly cytotoxic when it is converted into 5-fluoro-UMP (5-FUMP).Cells which lack CDase activity, either because of a mutation whichinactivates the gene encoding the enzyme or because they are naturallydeficient in this enzyme, as are mammalian cells, are resistant to 5-FC(JUND, et al. Journal of Bacteriology. 1970, no. 102, p. 607-15.;KILLSTRUP, et al. Journal of Bacteriology. 1989, no. 171, p.2124-2127.). By contrast, mammalian cells into which the sequencesencoding CDase activity were transferred became sensitive to 5-FC(HUBER, et al. Cancer Research. 1993, no. 53, p. 4619-4626.; MULLEN, etal. Proceedings of the National Academy of Sciences of the United Statesof America. 1992, no. 89, p. 33-37.; WO 93/01281 (US HEALTH)). Inaddition, the neighboring, untransformed cells also become sensitive to5-FC (HUBER, et al. Proceedings of the National Academy of Sciences ofthe United States of America. 1994, no. 91, p. 8302-6.). Thisphenomenon, which is termed a bystander effect, is due to the cellswhich are expressing the CDase activity secreting 5-FU, which thenintoxicates the neighboring cells by straightforward diffusion acrossthe plasma membrane. This property of 5-FU in diffusing passivelyrepresents an advantage as compared with the tk/GCV reference system,where the bystander effect requires there to be contact with the cellswhich are expressing tk (MESNIL, et al. Proceedings of the NationalAcademy of Sciences of the United States of America. 1996, no. 93, p.1831-35.). All the advantages which CDase offers within the context ofgene therapy, in particular anticancer gene therapy, can therefore bereadily understood.

The Saccharomyces cerevisiae (S. cerevisiae) FCY1, Candida Albicans FCA1and the E. coli codA genes, which respectively encode the CDase of thesetwo organisms, are known and their sequences have been published (SEQ IDNO:4; SEQ ID NO:5; SEQ ID NO:6 respectively).

With this respect, according to a more preferred embodiment of theinvention, the gene coding a protein having a CDase activity is FCY1,FCA1 or CodA or an analogue thereof. Analogues of these genes refers toa gene having an nucleic acid sequence which have at least a degree ofidentity greater than 70%, advantageously greater than 80%, preferablygreater than 90%, and most preferably greater than 95% with the nucleicacid sequence of the parent gene.

Patent WO 2005/007857 discloses a gene coding a protein having animproved CDase activity. This polypeptides derived from a native CDaseby addition of an amino acid sequence. According to another preferredembodiment of the invention, the protein having a CDase activity is apolypeptide disclosed WO 2005/007857 and more preferably the FCU1-8polypeptide represented in the sequence identifier SEQ ID NO:2 andanalogues thereof.

In prokaryotes and lower eukaryotes, uracil is transformed into UMP bythe action of uracil phosphoribosyl transferase (UPRTase). This enzymeconverts 5-FU into 5-FUMP. According to another preferred embodiment ofthe invention, the suicide gene codes a protein having an UPRTaseactivity.

The UPRTase in question may be of any origin, in particular ofprokaryotic, fungal or yeast origin. By way of illustration, the nucleicacid sequences encoding the UPRTases from E. coli (ANDERSEN, et al.Characterization of the upp gene encoding uracilphosphoribosyltransferase of Escherichia coli K12. European Journal ofBiochemistry. 1992, no. 204, p. 51-56.), from Lactococcus lactis(MARTINUSSEN, et al. Cloning and characterization of upp, a geneencoding uracil phosphoribosyltransferase from Lactococcus lactis.Journal of Bacteriology. 1994, vol. 176, no. 21, p. 6457-63.), fromMycobacterium bovis (KIM, et al. Complete sequence of the UPP geneencoding uracil phosphoribosyltransferase from Mycobacterium bovis BCG.Biochemistry and molecular biology international. 1997, vol. 41, no. 6,p. 1117-24.) and from Bacillus subtilis (MARTINUSSEN, et al. Two genesencoding uracil phosphoribosyltransferase are present in Bacillussubtilis. Journal of Bacteriology. 1995, vol. 177, no. 1, p. 271-4.) maybe used in the context of the invention. However, it is mostparticularly preferred to use a yeast UPRTase and in particular thatencoded by the S. cerevisiae FUR1 gene whose sequence disclosed in KERN,et al. The FUR1 gene of Saccharomyces cerevisiae: cloning, structure andexpression of wild-type and mutant alleles. (Gene. 1990, vol. 88, no. 2,p. 149-57.) is introduced here by way of reference. As a guide, thesequences of the genes and those of the corresponding UPRTases may befound in the literature and the specialist databanks (SWISSPROT, EMBL,Genbank, Medline and the like).

Application EP 0998568 A describes an FUR1 gene lacking 105 nucleotidesin 5′ of the coding part allowing the synthesis of a UPRTase from whichthe 35 first residues have been deleted at the N-terminal position andstarting with the methionine at position 36 in the native protein. Theproduct of expression of the mutant gene, designated FUR1Δ105, iscapable of complementing an fur1 mutant of S. cerevisiae. In addition,the truncated mutant exhibits a higher UPRTase activity than that of thenative enzyme. Thus, according to a particularly advantageous embodimentof the invention, the suicide gene codes a deletion mutant of a nativeUPRTase. The deletion is preferably located in the N-terminal region ofthe original UPRTase. It may be complete (affecting all the residues ofsaid N-terminal region) or partial (affecting one or more continuous ordiscontinuous residues in the primary structure). In general, apolypeptide consists of N-terminal, central and C-terminal parts, eachrepresenting about a third of the molecule. For example, since the S.cerevisiae UPRTase has 251 amino acids, its N-terminal part consists ofthe first 83 residues starting with the so-called initiator methioninesituated at the first position of the native form. As for the E. coliUPRTase, its N-terminal part covers positions 1 to 69.

A preferred protein having an UPRTase activity comprises an amino acidsequence substantially as represented in the sequence identifier SEQ IDNO: 1 of EP 0998568 A, starting with the Met residue at position 1 andending with the Val residue at position 216. The term “substantially”refers to a degree of identity with said sequence SEQ ID NO: 1 EP0998568 A greater than 70%, advantageously greater than 80%, preferablygreater than 90%, and most preferably greater than 95%. More preferablystill, it comprises the amino acid sequence represented in the sequenceidentifier SEQ ID NO: 1 EP 0998568 A. As mentioned above, it maycomprise additional mutations. There may be mentioned in particular thesubstitution of the serine residue at position 2 (position 37 in thenative UPRTase) by an alanine residue.

According to another preferred embodiment of the invention, the suicidegene codes a protein having at least one CDase and one UPRTase activity.Patent applications WO 96/16183 and EP 0998568 A describe the use of afusion protein encoding an enzyme with two domains having the CDase andUPRTase activities and demonstrate that the transfer of a hybrid genecodA::upp or FCY1::FUR1 or FCY1::FUR1Δ105 (i.e. FCU1) carried by anexpression plasmid increases the sensitivity of the transfected B16cells to 5-FC. According to a more preferred embodiment of theinvention, the suicide gene codes a polypeptide comprising an amino acidsequence substantially as represented in the sequence identifier SEQ IDNO:3 (coda::upp), SEQ ID NO:1 (FCU1) or FCY1::FUR1. The term“substantially” refers to a degree of identity with said sequencegreater than 70%, advantageously greater than 80%, preferably greaterthan 90%, and most preferably greater than 95%. More preferably still,it comprises the amino acid sequence as represented in the sequenceidentifier SEQ ID NO:3 (coda::upp), SEQ ID NO:1 (FCU1) or FCY1::FUR1. Asmentioned above, it may comprise additional mutations.

The nucleic acid sequences may be easily obtained by cloning, by PCR orby chemical synthesis according to the conventional techniques in use.They may be native genes or genes derived from the latter by mutation,deletion, substitution and/or addition of one or more nucleotides.Moreover, their sequences are widely described in the literature whichcan be consulted by persons skilled in the art.

Persons skilled in the art are capable of cloning the CDase or UPRTasesequences from the published data and of carrying out possiblemutations, of testing the enzymatic activity of the mutant forms in anacellular or cellular system according to the prior art technology orbased on the protocol indicated in application EP 0998568 A, and offusing, in particular in phase, the polypeptides with CDase and UPRTaseactivity, and consequently all or part of the corresponding genes.

According to a more preferred embodiment, the poxvirus of the inventionfurther comprises a nucleic acid sequence comprising a gene coding apermease.

Permease refers to transmembraneous protein involved in the transfer ofa drug comprising one nucleobase moiety, or a precursor thereof throughthe cell membrane.

Permease comprises but are limited to purine permease, cytosine permeaseand nucleoside transporters.

According to a preferred embodiment of the invention, permease is apurine or a cytosine permease of S. Cerevisiae. The nucleobasetransporters of S. cerevisiae consist of the purine-cytosine permease,known as FCY2, and the uracil permease, known as FUR4. Thepurine-cytosine permease, FCY2 mediates symport of protons and adenine,guanine, hypoxanthine and cytosine across the yeast plasma membrane(Grenson 1969, Jund and Lacroute 1970, Polak and Grenson 1973,Chevallier et al. 1975, Hopkins et al. 1988). FCY2 protein mediates alsothe transport of 5-fluorocytosine, an analogue of cytosine (Grenson1969, Jund and Lacroute 1970). FCY2 gene encodes a protein of 533 aminoacids (58 kDa) initially predicted to have 10-12 transmembrane-spanningdomains (Weber et al. 1990), with nine now favoured (Ferreira et al.1999). FCY2 exhibits similar affinities for the purine nucleobases andcytosine (Brethes et al. 1992). Uracil uptake into S. cerevisiae ismediated by the uracil permease, FUR4 (Jund and Lacroute 1970, Jund etal. 1977). FUR4 is a uracil-proton symporter (Hopkins et al. 1988)predicted to be a protein of 633 amino acids (71.7 kDa) with 10transmembrane domains and long cytoplasmic hydrophylic N- and C-terminaltails (Jund et al. 1988, Garnier et al. 1996). FUR4 protein can alsomediates the transport of 5-fluorouracil, an analogue of uracil (Jundand Lacroute 1970).

Amino acid sequences of FCY2 and Fur4 are notably available in theswissprot database (accession number P17064 and P05316 respectively).Preferably, permease has an amino acid sequence chosen from the groupcomprising amino acid sequence SEQ ID NO:1 and SEQ ID NO:2 as disclosedin patent application WO 2006/048768.

With this respect, according to a preferred embodiment of the invention,the permease is chosen from the group comprising FCY2 and Fur4 andanalogues thereof. Analogues of Fur4 and FCY2 refers to polypeptidehaving an amino acid sequence which have at least a degree of identitygreater than 70%, advantageously greater than 80%, preferably greaterthan 90%, and most preferably greater than 95% with the amino acidsequence of the parent protein as described here above and which retainsthe ability to transport a drug comprising one nucleobase moiety throughthe cell membrane.

The one skilled in the art is able to choose the permease which will beassociated with the drug or the precursor of the drug comprising onenucleobase moiety. For example, FCY2 and Fur4 are preferably associatedwith 5-Fluorocytosine (5-FC).

According to a more preferred embodiment, the poxvirus of the inventionmay further comprise the elements necessary for the expression of thenucleic acid of interest.

According to a more preferred embodiment, the poxvirus of the inventionmay further comprise the elements necessary for the expression of thenucleic acid sequence comprising a gene coding a permease.

These elements necessary for the expression of the nucleic acid ofinterest and/or the nucleic acid sequence comprising a gene coding apermease comprised the elements required for transcription of said DNAinto mRNA and, if necessary, for translation of mRNA into polypeptide.Transcriptional promoters suitable for use in various vertebrate systemsare widely described in literature. For example, suitable promotersinclude viral promoters like RSV, MPSV, SV40, CMV or 7.5 k, vacciniapromoter, inducible promoters, etc. Preferred promoters are isolatedfrom poxviruses e.g. 7.5K, HSR, TK, p28, p11 or K1L of vaccinia virus.Alternatively, one may use a synthetic promoter such as those describedin CHAKRABARTI. Biotechniques. 1997, no. 23, p. 1094-97., HAMMOND, etal. Journal of Virological Methods. 1997, no. 66, p. 135-38. and KUMAR.Virology. 1990, no. 179, p. 151-8. as well as chimeric promoters betweenearly and late poxviral promoters.

The nucleic acid sequence of interest and the nucleic acid sequencecomprising a gene coding a permease may further include additionalfunctional elements, such as intron sequences, targeting sequences,transport sequences, secretion signal, nuclear localization signal,IRES, poly A transcription termination sequences, tripartite leadersequences, sequences involved in replication or integration. Saidsequences have been reported in the literature and can be readilyobtained by those skilled in the art.

The invention also relates to a process for preparing a poxvirusaccording to the invention, in which process:

(i) a poxvirus according to the invention is introduced into a cell,

(ii) said cell is cultured under conditions which are appropriate forenabling said poxvirus to be produced, and

(iii) said poxvirus is recovered from the cell culture.

While the poxvirus can of course be recovered from the culturesupernatant, it can also be recovered from the cells. One of thecommonly employed methods consists in lysing the cells by means ofconsecutive freezing/thawing cycles in order to collect the virions inthe lysis supernatant. The virions can then be amplified and purifiedusing the techniques of the art (chromatographic method, method ofultra-centrifugation, in particular through a cesium chloride gradient,etc.).

The present invention, also relates to a composition which comprises apoxvirus according to the invention in combination with apharmaceutically acceptable excipient.

A composition according to the invention is more specifically intendedfor the preventive or curative treatment of diseases by means of genetherapy and is more specifically aimed at proliferative diseases(cancers, tumors, restenosis, etc.) or aimed at diseases associated toan increased osteoclast activity (e.g. rheumatoid arthritis,osteoporosis).

A composition according to the invention can be made conventionally witha view to administering it locally, parenterally or by the digestiveroute. In particular, a therapeutically effective quantity of therecombinant vector or poxvirus of the invention is combined with apharmaceutically acceptable excipient. It is possible to envisage alarge number of routes of administration. Examples which may bementioned are the intragastric, subcutaneous, intracardiac,intramuscular, intravenous, intraperitoneal, intratumor, intranasal,intrapulmonary and intratracheal routes. In the case of these threelatter embodiments, it is advantageous for administration to take placeby means of an aerosol or by means of instillation. The administrationcan take place as a single dose or as a dose which is repeated on one ormore occasions after a particular time interval. The appropriate routeof administration and dosage vary depending on a variety of parameters,for example the individual, the disease to be treated or the gene(s) ofinterest to be transferred. The preparations based on viral particlesaccording to the invention can be formulated in the form of doses ofbetween 10⁴ and 10¹⁴ pfu (plaque-forming units), advantageously 10⁵ and10¹³ pfu, preferably 10⁶ and 10¹² pfu, more preferably 10⁶ and 10⁷.

The composition can also include a diluent, an adjuvant or an excipientwhich is acceptable from the pharmaceutical point of view, as well assolubilizing, stabilizing and preserving agents. In the case of aninjectable administration, preference is given to a formulation in anaqueous, non-aqueous or isotonic solution. It can be presented as asingle dose or as a multidose, in liquid or dry (powder, lyophilizate,etc.) form which can be reconstituted at the time of use using anappropriate diluent.

The present invention also relates to the use of a poxvirus or acomposition according to the invention for preparing a medicament whichis intended for treating the human or animal body by gene therapy. Themedicament can be administered directly in vivo (for example byintravenous injection, into an accessible tumor, into the lungs by meansof an aerosol, into the vascular system using an appropriate catheter,etc.). A preferred use consists in treating or preventing cancers,tumors and diseases which result from unwanted cell proliferation.Conceivable applications which may be mentioned are cancers of thebreast, of the uterus (in particular those induced by papillomaviruses), of the prostate, of the lung, of the bladder, of the liver, ofthe colon, of the pancreas, of the stomach, of the oesophagus, of thelarynx, of the central nervous system (e.g. glioblastoma) and of theblood (lymphomas, leukemia, etc.). An other preferred use consists intreating or preventing rheumatoid arthritis, osteoporosis and otherdiseases associated to an increased osteoclast activity. It can also beused in the context of cardiovascular diseases, for example in order toinhibit or retard the proliferation of the smooth muscle cells of theblood vessel wall (restenosis). Finally, in the case of infectiousdiseases, it is possible to conceive of the medicament being applied toAIDS.

When the poxvirus, composition or method of the invention is used forthe treatment of cancer, the preferred route of administration is thesystemic route since the poxvirus according to the invention is able tospecifically target the tumoral cells.

The invention also extends to a method for treating diseasescharacterized in that a poxvirus, a composition according to theinvention is administered to an host organism or cell which is in needof such treatment.

According to an advantageous embodiment, the therapeutic use or thetreatment method also comprises an additional step in whichpharmaceutically acceptable quantities of a prodrug, advantageously ananalog of cytosine, in particular 5-FC, are administered to the hostorganism or cell. By way of illustration, it is possible to use a doseof from 50 to 500 mg/kg/day, with a dose of 200 mg/kg/day or of 100mg/kg/day being preferred. Within the context of the present invention,the prodrug is administered in accordance with standard practice (e.g.per os, systematically).

Preferably, the administration taking place subsequent to theadministration of the therapeutic agent according to the invention,preferably at least 3 days, more preferably at least 4 days and evenmore preferably at least 5 days after the administration of thetherapeutic agent. According to an even more preferred embodiment of theinvention, the administration of the prodrug takes place 7 days afterthe administration of the therapeutic agent. The oral route ispreferred. It is possible to administer a single dose of prodrug ordoses which are repeated for a time which is sufficiently long to enablethe toxic metabolite to be produced within the host organism or cell.

Furthermore, the composition or method according to the invention can becombined with one or more substances which potentiate the cytotoxiceffect of the 5-FU. Mention may in particular be made of drugs whichinhibit the enzymes of the pathway for the de novo biosynthesis of thepyrimidines (for example those mentioned below), drugs such asLeucovorin (Waxman et al., 1982, Eur. J. Cancer Clin. Oncol. 18,685-692), which, in the presence of the product of the metabolism of5-FU (5-FdUMP), increases the inhibition of thymidylate synthase,resulting in a decrease in the pool of dTMP, which is required forreplication, and finally drugs such as methotrexate (Cadman et al.,1979, Science 250, 1135-1137) which, by inhibiting dihydrofolatereductase and increasing the pool of PRPP (phosphoribosylpyrophosphate),brings about an increase in the incorporation of 5-FU into the cellularRNA.

According to the present invention, the drugs which inhibit the enzymesof the pathway for the de novo biosynthesis of the pyrimidines arepreferably selected from the group consisting of PALA(N-(phosphonoacetyl)-L-aspartate; Moore et al., 1982, Biochem.Pharmacol. 31, 3317-3321), Leflunomide, A771726 (active metabolite ofLeflunomide; Davis et al., 1996, Biochem. 35, 1270-1273) and Brequinar(Chen et al., 1992, Cancer Res. 52, 3251-3257).

The composition or method according to the invention can be combinedwith one or more substances effective in anticancer therapy. Amongpharmaceutical substances effective in anticancer therapy which may beused in association or in combination with the compositions according tothe invention, there may be mentioned alkylating agents such as, e.g.,mitomycin C, cyclophosphamide, busulfan, ifosfamide, isosfamide,melphalan, hexamethylmelamine, thiotepa, chlorambucil, or dacarbazine;antimetabolites such as, e.g., gemcitabine, capecitabine,5-fluorouracil, cytarabine, 2-fluorodeoxy cytidine, methotrexate,idatrexate, tomudex or trimetrexate; topoisomerase II inhibitors suchas, e.g., doxorubicin, epirubicin, etoposide, teniposide ormitoxantrone; topoisomerase I inhibitors such as, e.g., irinotecan(CPT-11), 7-ethyl-10-hydroxy-camptothecin (SN-38) or topotecan;antimitotic drugs such as, e.g., paclitaxel, docetaxel, vinblastine,vincristine or vinorelbine; and platinum derivatives such as, e.g.,cisplatin, oxaliplatin, spiroplatinum or carboplatinum.

The one or more substances effective in anticancer therapy and thecomposition of the invention may be administered once or several timesby methods well known to the skilled practitioner including systemicadministration and direct injection into the tumor. One may proceed bybolus injection or perfusion (e.g. over 0.5-6 hours). The variousadministrations of the anti-cancer substance and/or the poxviruscomposition can be separated each other by an appropriate period of timeand carried out by the same route or by different routes ofadministrations at the same site or at different sites using the same ordifferent dosages. The dosage may be adapted by the practitioner inlight of various parameters such as the nature of the cancer to betreated, the mode and the frequency of administration(s), and otherfactors routinely considered in administering a drug.

In one embodiment, the method or composition of the invention iscombined with a topoisomerase I inhibitor with a specific preference foririnotecan. Preferably, irinotecan and the poxvirus composition will beadministered intravenously. By way of illustration, suitable doses foririnotecan may vary from 5 to 100 mg/kg/day and those for poxvirus from1×10⁶ to 1×10⁹ pfu. Preferably, poxvirus composition will be injectedonce to three times intravenously and irinotecan at a suitableperiodicity (e.g. once a week) for one or more cycles. Additionally,irinotecan treatment will be carried out a few days (e.g. 3 to 10 days)after the first administration of the poxvirus composition.

In another embodiment, the method or composition of the invention iscombined with an antimitotic drug with a specific preference foroxaliplatin. Preferably, oxaliplatin will be administeredintraperitonally or intravenously and the poxvirus composition accordingto the invention by intravenous route. By way of illustration, suitabledoses for oxaliplatin may vary from 0.5 to 10 mg/kg/day and those forpoxvirus from 1×106 to 1×109 pfu. Preferably, poxvirus composition willbe injected once to three times intravenously and oxaliplatin at asuitable periodicity (e.g. every two weeks) for one or more cycles.Additionally, a preferred method comprises first the administration ofthe poxvirus composition followed by oxaliplatin treatment few days(e.g. 3 to 10 days) after the first poxvirus injection.

Furthermore, the method or composition of the invention also comprisesan additional step in which pharmaceutically acceptable quantities of aprodrug are administered to the host organism or cell as describedabove. A preferred prodrug in the context of the invention is 5-FC.

The compositions or methods according to the invention can also be usedin combination with radiotherapy.

The compositions or methods according to the invention may also be usedin combination with one or more other agents including but not limitedto immunomodulatory agents such as, e.g. alpha, beta or gammainterferon, interleukin (in particular IL-2, IL-6, IL-10 or IL-12) ortumor necrosis factor; agents that affect the regulation of cell surfacereceptors such as, e.g. inhibitors of Epidermal Growth Factor Receptor(in particular cetuximab, panitumumab, zalutumumab, nimotuzumab,matuzumab, gefitinib, erlotinib or lapatinib) or inhibitors of HumanEpidermal Growth Factor Receptor-2 (in particular trastuzumab); andagents that affect angiogenesis such as, e.g. inhibitor of VascularEndothelial Growth Factor (in particular bevacizumab or ranibizumab).

BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS

FIG. 1. In vitro Sensitivities to 5-FC of vaccinia viruses infectedhuman colorectal tumor cells (LoVo). LoVo cells, infected at a MOI of0.0001 with the indicated viruses (mock (●) VVTK-/FCU1 (▪) orVVTK-I4L-/FCU1 (Δ)) were exposed to various concentration of 5-FC. Cellsurvival was measured at 5 days post-infection. Results were expressedin percentage of cellular viability in the presence or not of drugs.Values are represented in mean±SD of three individual determinationswithout the cell mortality due to the replication of the viruses.

FIG. 2. In vitro Sensitivities to 5-FC of vaccinia viruses infectedhuman colorectal tumor cells (LoVo). LoVo cells, infected at a MOI of0.0001 with the indicated viruses (mock (●) VVTK-/FCU1 (▪) orVVTK-F4L-/FCU1 (⋄) were exposed to various concentration of 5-FC. Cellsurvival was measured at 5 days post-infection. Results were expressedin percentage of cellular viability in the presence or not of drugs.Values are represented in mean±SD of three individual determinationswithout the cell mortality due to the replication of the viruses.

FIG. 3. In vitro replication efficacy of VVTK-/FCU1 and VVTK-I4L-/FCU1in LoVo infected at a MOI of 0.0001 with the indicated viruses at day 5post infection. Values are represented in mean±SD of three individualdeterminations.

FIG. 4. In vitro replication efficacy of VVTK-/FCU1 and VVTK-F4L-/FCU1in LoVo infected at a MOI of 0.0001 with the indicated viruses at day 5post infection. Values are represented in mean±SD of three individualdeterminations.

FIG. 5. Mean tumor volume±SEM of s.c LoVo in Swiss nude mice after i.vinjection of virus. 7 days after inoculation with tumor (palpabletumor), mice were treated by 10⁷ pfu of buffer+saline (⋄), buffer+5-FC(♦), VVTK-I4L-/FCU1+saline (Δ) or VVTK-I4L-/FCU1+5-FC (▴). The animalswere treated by saline or 5-FC at 100 mg/kg/j twice a day by oralgavage, 7 days after virus injection during 3 weeks. Tumor volume wasmeasured twice a week.

FIG. 6. Mean tumor volume±SEM of s.c LoVo in Swiss nude mice after i.vinjection of virus. 7 days after inoculation with tumor (palpabletumor), mice were treated by 10⁷ pfu of buffer+saline (⋄), buffer+5-FC(♦), VVTK-F4L-/FCU1+saline (□) or VVTK-F4L-/FCU1+5-FC (a). The animalswere treated by saline or 5-FC at 100 mg/kg/j twice a day by oralgavage, 7 days after virus injection during 3 weeks. Tumor volume wasmeasured twice a week.

FIG. 7. Mean tumor volume±SEM of s.c LoVo in Swiss nude mice after i.vinjection of virus. 11 days after inoculation with tumor (palpabletumor), mice were treated by buffer+H₂O(⋄), or buffer+5-FC (♦), or oneinjection of 10⁷ pfu of VVTK-I4L-/FCU1+H₂O(◯), or one injection of 10⁷pfu of VVTK-I4L-/FCU1+5-FC (5-FC administrated 7 days after virusinjection and during 3 weeks) (●), or two injections (day 11 and day 33)of 10⁷ pfu of VVTK-I4L-/FCU1+H₂O (□), or two injections (day 11 and day33) of 10⁷ pfu of VVTK-I4L-/FCU1+5-FC (5-FC administrated from day 18 today 32 and from day 40 to day 54) (▪). The animals were treated by 5-FCat 100 mg/kg twice a day by oral gavage. Tumor volume was measured twicea week.

FIG. 8. Mean tumor volume±SEM of s.c U87-MG (glioblastoma tumor cells)in Swiss nude mice after i.v injection of virus. 11 days afterinoculation with tumor (palpable tumor), mice were treated by buffer+H₂O(⋄), or buffer+5-FC (♦), or 10⁷ pfu of VVTK-I4L-/FCU1+H₂O (◯), or 10⁷pfu of VVTK-I4L-/FCU1+5-FC (●). The animals were treated by 5-FC at 100mg/kg twice a day by oral gavage, 7 days after virus injection andduring 3 weeks. Tumor volume was measured twice a week.

FIG. 9. Ratio of virus yield in dividing cells versus in confluentcells. PANC1 (pancreatic human tumor), H1299 (Lungs human tumor) orU118MG (glioma human tumor) cells are infected with 100 pfu of (▮)VVTK-/FCU1 or (

) VVTK-I4L-/FCU1. 48 h post-infection, viral titers were determined.Values are the ratio between yields of virus in dividing cells versus inconfluent cells.

FIG. 10. Ratio of virus yield in dividing cells versus in confluentcells. PANC1 (pancreatic human tumor), H1299 (Lungs human tumor) orU118MG (glioma human tumor) cells are infected with 100 pfu of (▮)VVTK-/FCU1 or (

) VVTK-F4L-/FCU1. 48 h post-infection, viral titers were determined.Values are the ratio between yields of virus in dividing cells versus inconfluent cells.

FIG. 11. Viral titers (pfu/mg of tissue) in organs or tumors at day 6and day 21 after i.v. infection into Swiss nude mice bearingsubcutaneous human tumors with 1×10⁶ PFU of VVTK-/FCU1 (▮) orVVTK-I4L-/FCU1 (

).

FIG. 12. Viral titers (pfu/mg of tissue) in organs or tumors at day 6and day 21 after i.v. infection into Swiss nude mice bearingsubcutaneous human tumors with 1×10⁶ PFU of VVTK-/FCU1 (▮) orVVTK-F4L-/FCU1 (

).

FIG. 13. Survival of Swiss nude mice after treatment with 1×10$ pfu ofVVTK-/FCU1 (▪) or VVTK-I4L-/FCU1 (◯) by i.v injection.

FIG. 14. Survival of immunocompetent B6D2 mice after treatment with1×10⁷ pfu (A) or 1×10⁸ pfu (B) of VVTK-/FCU1 (▪) or VVTK-I4L-/FCU1 (⋄)by i.v injection.

FIG. 15. Average quantity of pocks on tails after i.v injection of 1×10⁶pfu VVTK-/FCU1 or VVTK-I4L-/FCU1 in Swiss nude mice at day 13post-infection and at day 34 post-infection.

FIG. 16. Average quantity of pocks on tails after i.v injection of 1×10⁶pfu VVTK-/FCU1 or VVTK-F4L-/FCU1 in Swiss nude mice at day 13post-infection and at day 34 post-infection.

FIG. 17. Average quantity of pocks on tails after i.v injection of 1×10⁷pfu VVTK-/FCU1 or VVTK-I4L-/FCU1 in Swiss nude mice at day 15post-infection and at day 31 post-infection.

FIG. 18. Average quantity of pocks on tails after i.v injection of 1×10⁷pfu VVTK-/FCU1 or VVTK-F4L-/FCU1 in Swiss nude mice at day 15post-infection and at day 31 post-infection.

MODE(S) FOR CARRYING OUT THE INVENTION Examples

Construction of Vector Plasmids

A shuttle plasmid for deleting I4L was constructed using the DNA ofvaccinia virus strain Copenhagen (accession number M35027) deleted onThymidine Kinase gene and expressing FCU1 gene under the control ofvaccinia synthetic promoter p11K7.5. The DNA flanking regions of I4Lwere amplified by PCR. Primers of the downstream flanking region of I4Lwere 5′-TCC CCC GGG TTA ACC ACT GCA TGA TGT ACA-3′ (SEQ ID NO:7; SmaIsite underlined) and 5′-GCC GAG CTC GAG GTA GCC GTT TGT AAT TCT-3′ (SEQID NO:8; SacI site underlined). Primers for the upstream region were5′-GCC TGG CCA TAA CTC CAG GCC GTT—3′ (SEQ ID NO:9; MscI siteunderlined) and 5′-GCC CAG CTG ATC GAG CCG TAA CGA TTT TCA-3′ (SEQ IDNO:10; PvuII site underlined). The amplified DNA fragment were digestedwith restriction enzyme SmaI/SacI or MscI/PvuII and ligated into thecorresponding sites in PpolyIII plasmid. A repeat region of thedownstream flanking region of I4L was amplified by PCR using the primers5′-GCC GCA TGC ATC CTT GAA CAC CAA TAC CGA-3′ (SEQ ID NO:11; SphI siteunderlined) and 5′-GCT CTA GAG AGG TAG CCG TTT GTA ATC TG-3′ (SEQ IDNO:12; XbaI site underlined) and inserted in PpolyIII plasmid. Therepeat region is used to eliminate the selection cassette during theproduction of deleted viruses. The selection cassette, corresponding tothe GFP/GPT fusion gene under the control of pH5R vaccinia promoter, wasinserted into the SacI/SphI site in PpolyIII plasmid. The obtainedplasmid is the recombinant shuttle plasmid named pΔI4L for deletion ofI4L gene.

A shuttle plasmid for deleting F4L was constructed using the DNA ofvaccinia virus strain Copenhagen (accession number M35027). The DNAflanking regions of F4L were amplified by PCR. Primers of the downstreamflanking region of F4L were 5′-CGC GGA TCC TTT GGT ACA GTC TAG TATCCA-3′ (SEQ ID NO:13; BamHI site underlined) and 5′-TCC CCC GGG TTA TAACAG ATG CAG TAT CCA-3′ (SEQ ID NO:14; SmaI site underlined). Primers forthe upstream region were 5′-GCC CAG CTG TTC AAT GGC CAT CTG AAA TCC-3′(SEQ ID NO:15; PvuII site underlined) and 5′-GAA GAT CTA GTA TCG CAT CTAAAA GAT GG-3′ (SEQ ID NO:16; BgIII site underlined). The amplified DNAfragment were digested with restriction enzyme BamHI/SmaI or BgIII/PvuIIand ligated into the corresponding sites in PpolyIII plasmid. A repeatregion of the downstream flanking region of I4L was amplified by PCRusing the primers 5′-GCC GAG CTC ACC CAC ACG TTT TTC GAA AAA-3′ (SEQ IDNO:17; SacI site underlined) and 5′-GCC GCA TGC TTA TAA CAG ATG CAG TATCAA-3′ (SEQ ID NO:18; SphI site underlined) and inserted in PpolyIIIplasmid. The repeat region is used to eliminate the selection cassetteduring the production of deleted viruses. The selection cassette,corresponding to the GFP/GPT fusion gene under the control of pH5Rvaccinia promoter, was inserted into the SacI/SmaI site in PpolyIIIplasmid. The obtained plasmid is the recombinant shuttle plasmid namedpΔF4L for deletion of F4L gene.

The Generation of Recombinant Vaccinia Viruses.

CEF cells were infected with VVTK-FCU1 (Vaccinia virus, defective forthe J2R Kinase gene, expressing FCU1 gene under the control of syntheticpromoter p11k7.5) strain Copenhagen at a MOI of 0.1 and incubated at 37°C. for 2 h, then transfected with a CaCl₂ coprecipitate of therecombinant shuttle plasmid (0.2 μg). The cells were incubated for 48 hat 37° C. Dilutions of virus emerging were then used to infect the CEFcells in selection medium containing Hypoxanthine at final concentrationof 15 μg/ml, xanthine at final concentration of 250 μg/ml andmycophenolic acide at final concentration of 250 μg/ml. Fluorescent(GFP) and positive (GPT selection) plaques were isolated and selectedfor a several round of selection in CEF cells in presence of GPTselection medium. The presence or not of VVTK-FCU1 was determined by 40cycles of PCR with primers inside the deletion region. After theelimination of parental virus, the double deleted virus was used toinfect CEF without GPT selection medium to eliminate the selectioncassette. Non-fluorescent plaques were isolated and selected for 2cycles in CEF. Final recombinant VV viruses were amplified in CEF,purified and virus stocks were titrated on CEF by plaque assay.

In Vitro Cell Sensitivity to 5-FC.

Human tumor cells were transduced by the respective recombinant VV at aMOI of 0.0001. A total of 3×10⁵ cells/well were plated in 6-well culturedishes in 2 ml of medium containing various concentrations of 5-FC.Cells were then cultured at 37° C. for 5 days, and the viable cells werecounted by trypan blue exclusion. Results depicted in FIGS. 1, 2, 3 and4 shows that the FCU1 activity is equivalent in viruses defective forthe J2R gene than in viruses defective for the I4L and J2R gene or thanin viruses defective for the F4L and J2R gene.

In Vitro Replication in Cultured Cells.

Dividing or confluent cells were infected, in 6-wells plaques, at 100PFU of viruses (nearly MOI 0.0005). 2 mL of medium supplemented with 10%FCS for dividing cells and no supplemented for confluent cells wereadded. The cells were harvested at 48 hours post-infection. The cellswere stored at −20° C. and sonicated to release the virus, virus wasalso quantified by plaque titration on CEF cells. The ratio betweenreplication in dividing cells and confluent cells are similar in allcells. Both viruses VVTK-/FCU1, VVTK-I4L-/FCU1 and VVTK-F4L-/FCU1replicate more in dividing cells than in confluent cells.

As an indirect mean to assay for replication virus specificity, theyield of virus produced in dividing versus confluent tumor cells(pancreatic human tumor PANC1; lung human tumor H1299; glioma humantumor U118MG) was determined. Confluent cells were plated at 1×10⁶cells/well and cultured in complete media for 7 days then 1 day beforeinfection the cells were washed and cultured in media without serum.Dividing cells were plated at 3×10⁵ cells/well one day before infection.To evaluate the level of cell division, the amount of titrated thymidineincorporated into nucleic acid was measured 5 hours, 24 hours and 48hours after plating cells. During this period thymidine incorporationwas relatively constant in confluent cells whereas in dividing cells anincrease in incorporation was seen over time. Then the cells wereinfected with 100 pfu of viruses, and 48 h post infection the ratiobetween the yield of virus produced in dividing tumor cells and inconfluent tumor cells was determined by plaque titration on CEF. Resultsdepicted in FIGS. 9 and 10 show that both viruses VVTK-/FCU1,VVTK-I4L-/FCU1 and VVTK-F4L-/FCU1 replicate more in dividing cells thanin confluent cells. Results depicted in FIGS. 9 and 10 show moreover anincrease of ratio in all the different types of cells for both virusesVVTK-I4L-/FCU1 and VVTK-F4L-/FCU1 by comparison with VVTK-/FCU1. Thisincrease of ratio in all the different types of cells is due to a lowerreplication of both viruses VVTK-I4L-/FCU1 and VVTK-F4L-/FCU1 inconfluent cells. These results demonstrate that both virusesVVTK-I4L-/FCU1 and VVTK-F4L-/FCU1 display an increased specificitytoward dividing cells compared to VVTK-/FCU1.

Subcutaneous Tumor Model.

Female Swiss nude mice were obtained from Charles River Laboratories.Animals used in the studies were uniform in age (6 weeks) and bodyweights ranged from 23-26 g. Swiss nude mice were injectedsubcutaneously (s.c.) into the flank with 5×10⁶ LoVo cells. When tumorsreached a diameter of 50-70 mm³, the mice were randomized in a blindedmanner and treated with the indicated vectors for the in vivoexperiments.

Biodistribution of the Virus.

The presence of the various viruses was evaluated by virus titration intumors and organ samples. 1×10⁶ PFU of VV-FCU1 or VVTK-I4L-/FCU1 orVVTK-F4L-/FCU1 was injected intravenously (i.v.) by tail vein injectioninto nude mice bearing established s.c. LoVo tumors. Mice weresacrificed at indicated time points, and the tumors and other organswere collected and weighted. Tumors and organs were homogenized in PBSand titers were determined on CEF as described previously. Viral titerswere standardized to milligram of tissue. Viral titers were standardizedto milligram of tissue. Results depicted in Table 2, 3, 4 and 5 (therange of virus titers is presented in pfu/mg of tissue) show that after14 days the virus according to the invention is mostly found in thetumor. Results depicted in FIGS. 11 and 12 show that both virusesVVTK-/FCU1, VVTK-I4L-/FCU1 and VVTK-F4L-/FCU1 target the tumor withabout 1 000 to 10 000 fold more virus in the tumor than in the otherorgans analyzed except for tails in the case of VVTK-/FCU1. A smallamount of VVTK-/FCU1 is detected in lungs, spleen, kidney and lymphnodes (less than 10 pfu/mg) and more in skin, tail and bone marrow atday 6, and skin and tail at day 21. In contrast, both VVTK-I4L-/FCU1 andVVTK-F4L-/FCU1 have higher tumor specificity with only a small amount inlymph nodes and tail at day 6, and only in tumor at day 21.

TABLE 2 Tumor Lungs Spleen Kidney L.Nodes Heart VVTK- (0.2-3.3) × 0.1-20-2.2 0-1.8 0-61 0-0.3 /FCU1 10⁵ VVTK- 25.6-2.2 ×    0-0.1 n.d 0-1   n.dn.d I4L/FCU1 10⁵

TABLE 3 Bone Ovaries Skin Tail Marrow Brain Muscles VVTK-/ 2.2-74  0.1-24 13.5-7 · 10⁴ 0-800 0-1.8 0-22 FCU1 VVTK- 0-102 n.d 26.3 n.d n.dn.d I4L/FCU1

TABLE 4 Tumor Lungs Spleen Kidney L.Nodes Ovaries VVTK- (0.2-3.3) ×0.1-2 0-2.2 0-1.8 0-61 2.2-74 /FCU1 10⁵ VVTK- 51.8-3.8 × n.d n.d n.d 0-2.1 n.d F4L/FCU1 10⁴

TABLE 5 Bone Tail Marrow Intestine Brain Muscles Heart VVTK- 13.5-7 ·10⁴ 0-800 n.d 0-1.8 0-22 0-0.3 /FCU1 VVTK-   0-7.9 n.d n.d n.d n.d n.dF4L/FCU1Antitumor Activity of the Poxvirus of the Invention in s.c. Tumor Model.

Nude mice bearing established s.c. LoVo tumors (50-70 mm³) were treatedone time intravenously (by tail vein) with the indicated vectors at doseof 1.10⁷ PFU, respectively. Starting day 7 following viral injection,5-FC was given by oral gavage at 100 mg/kg (0.5 ml 5-FC 0.5% in water)twice a day for 3 weeks. Tumor size was measured twice weekly usingcalipers. Tumor volume were calculated in mm³ using the formula (p/6)(length×width²). The results depicted in FIGS. 5 and 6 show that thevariouses viruses have a similar efficacy with an oncolytic activity(p<0.05) able to control the growth of tumor, and a combined activity(oncolytic of the virus and therapeutic of FCU1 gene) withadministration of 5-FC which can further improve the control of thetumor growth (p<0.01).

Nude mice bearing established s.c. LoVo tumors (50-70 mm³) were alsotreated intravenously (by tail vein) with the indicated vectors at doseof 1.10⁷ PFU according to the followings: 11 days after inoculation withtumor (palpable tumor), mice were treated by buffer+H₂O, or buffer+5-FC,or one injection of 10⁷ pfu of VVTK-I4L-/FCU1+H₂O, or one injection of10⁷ pfu of VVTK-I4L-/FCU1+5-FC (5-FC administrated 7 days after virusinjection and during 3 weeks), or two injections (day 11 and day 33) of10⁷ pfu of VVTK-I4L-/FCU1+H₂O, or two injections (day 11 and day 33) of10⁷ pfu of VVTK-I4L-/FCU1+5-FC (5-FC administrated from day 18 to day 32and from day 40 to day 54). The animals were treated by 5-FC at 100mg/kg twice a day by oral gavage. Tumor size was measured twice weeklyusing calipers. Tumor volume were calculated in mm³ using the formula(pl6) (length×width²). The results depicted in FIG. 7 show that noantitumoral activity of virus alone after one or two injections. Theaddition of 5-FC treatment shows statistically significant inhibition oftumor growth (p<0.05) when compared with vehicle groups and virus alone(without 5-FC) until day 50. As with one single injection, two i.v.injections of VVTK-I4L-/FCU1+5-FC demonstrates a significant antitumoralactivity when compared with vehicule groups and two injections of virusalone (without 5-FC) (p<0.05). Moreover, a significant difference ontumor evolution is observed from day 56 between one and two injectionsof virus in combination of 5-FC treatment (p<0.05).

Nude mice bearing established s.c. U87-MG (glioblastoma tumor cells)were treated intravenously (by tail vein) with the indicated vectors atdose of 1.10⁷ PFU according to the followings: 11 days after inoculationwith tumor (palpable tumor), mice were treated by buffer+H₂O, orbuffer+5-FC, or 10⁷ pfu of VVTK-I4L-/FCU1+H₂O, or 10⁷ pfu ofVVTK-I4L-/FCU1+5-FC. The animals were treated by 5-FC at 100 mg/kg twicea day by oral gavage, 7 days after virus injection and during 3 weeks.Tumor size was measured twice weekly using calipers. Tumor volume werecalculated in mm³ using the formula (π/6) (length×width²). The resultsdepicted in FIG. 8 show a high oncolytic activity of the VVTK-I4L-/FCU1on U87-MG cells which result in a strong antitumor activity (p<0.0001).The combined activity with addition of 5-FC, by oral gavage, results insimilar activity (p<0.0001).

Viral Pathogenicity.

Viral pathogenicity was assessed with survival studies done on bothSwiss nude mice (FIG. 13) and immunocompetents B6D2 mice (FIG. 14). Micewere injected I.V. with 1.10⁷ or 1.10⁸ PFU of all VVTK-/FCU1 andVVTK-I4L-/FCU1 in 100 μL of Buffer per mouse. Mice were observed dailythroughout the course of the experiment. In Swiss nude mice (FIG. 13),the injection of 1×10⁸ PFU of VVTK-/FCU1 results in the death of 40% ofthe animals 3 days after infection. The remaining mice died between day50 and day 80 after infection. The administration of VVTK-I4L-/FCU1 wasless pathogenic, the majority of the animals died between day 65 to 140(p<0.01). No evidence of toxicity has been observed with both viruses at10⁷ pfu (FIG. 14 (A)). All mice died after i.v injection of 10⁸ pfu ofVVTK-/FCU1 (FIG. 14 (B)). The group with treatment of VVTK-I4L-/FCU1 hadsignificantly prolonged survival to 70% compared with the VVTK-/FCU1infected mice (FIG. 14 (B)). Therefore, this result demonstrates thedecrease of toxicity with the double-deleted virus VVTK-I4L-/FCU1.

Pocks Tail Lesion Model.

Swiss nude mice were injected I.V. with 1.10⁶ (FIGS. 15 and 16) or 1.10⁷(FIGS. 17 and 18) PFU of each virus. Tail lesions were enumerated once aweek. Mice injected with 1.10⁶ PFU of VVTK-I4L-/FCU1 or VVTK-F4L-/FCU1have less than 1 pock/mice compared with mice injected with VVTK-/FCU1with a average of 8 pocks by mice in day 13 post-infection (p<0.001) asshown in FIG. 15 (A) and FIG. 16 (A). The results are similar at day 34post-injection with an average of 4 pocks with VVTK-/FCU1 compared tonearly 1 for VVTK-I4L-/FCU1 or VVTK-F4L-/FCU1 (p<0.0001) as shown inFIG. 15 (B) and FIG. 16 (B). Mice injected with 1.10⁷ PFU ofVVTK-I4L-/FCU1 or VVTK-F4L-/FCU1 have respectively an average of 3pocks/mice and 2 pocks/mice compared to mice injected with 1.10⁷ PFU ofVVTK-/FCU1 having an average of 10 pocks/mice at day 15 post-infection(FIG. 17 (A) and FIG. 18 (A)). At day 31 post-infection mice injectedwith VVTK-I4L-/FCU1 or VVTK-F4L-/FCU1 have respectively an average of1.5 pock/mice and 2 pocks/mice compared to mice injected with VVTK-/FCU1having an average of 7 pocks/mice (FIG. 17 (B) and FIG. 18 (B)). Thedifference in pock number between VVTK-/FCU1 and both VVTK-I4L-/FCU1 andVVTK-F4L-/FCU1 is statistically significant (p<0.01). The pocksformation is correlated with the replication of virus in the tail and sowith virulence and toxicity. Injection in i.v of VVTK-I4L-/FCU1 orVVTK-F4L-/FCU1 is less toxic than with the single deleted TK virus.

Combination VVTK-I4L-/FCU1 and Irinotecan

The therapeutic effects of VVTK-I4L-/FCU1 treatment in combination withirinotecan were evaluated in vivo on human pancreas cancer MiaPaca2 cellline (ATCC® number: CRL-1420™) in the presence and absence of 5FCprodrug. More specifically, nude mice (n=12 mice/group) were injectedsubcutaneously with 5×106 MiaPaca2 cells. When the tumors had 100-200mm3, VVTK-I4L-/FCU1 was injected intravenously at 1×106 PFU on days 24,28 and 30 post tumor implantation. Irinotecan was administeredintravenously at 33 mg/kg/day on days 28, 31, 35, 38, 42, 45. Startingon day 31 post tumor implantation, 5-FC was given by oral gavage at 100mg/kg twice a day for 3 weeks. Tumor size was measured using calipers.Tumor volume was calculated in mm3 using the formula (π/6)(length×width2). Mice were killed when tumor size exceeded 4000 mm3 involume. Mann-Whitney U-tests were used to determine tumor volumedifferences between the groups. A P-value <0.05 was consideredsignificant.

Tumor volume of human pancreatic MiaPaca2 implanted tumors were measuredregularly (every 4-6 days) after systemic injection ofVVTK-I4L-/FCU1+/−5-FC and irinotecan over a period of 73 days post tumorimplantation days. Table 6 provides the mean of tumor volumes in mm3measured in the various mice groups at 24, 39, 50, 59, 63 and 73 daysafter implantation. “iri” represents irinotecan and “VV” VVTK-I4L-/FCU1.

TABLE 6 Group D24 D39 D50 D59 D63 D73 Control 202 533 1395 1865 2876 †Iri 195 245 122 118 157 719 5-FC 218 561 1165 2484 2832 † Iri + 5FC 192217 113 197 253 634 VV 205 438 572 1371 1639 2265 VV + iri 189 217 88 7471 66 VV + 5FC 192 303 490 1211 2067 2451 VV + iri + 197 225 78 69 71 965FC †: Mice euthanized when tumor volume is >4000 mm³.

In MiaPaca2 model, in terms of tumor growth, there was no differencebetween the control (untreated) group and the group with 5-FC alone.Administration of VVTK-I4L-/FCU1 with or without 5-FC resulted in aslight antitumor effect. Administration of irinotecan with or without5-FC displayed a significant tumor growth control compared with notreatment. The greatest benefit in terms of tumor growth control wasseen with VVTK-I4L-/FCU1 in combination with irinotecan and this with orwithout 5-FC administration.

In conclusion, treatment with the combination of VVTK-I4L-/FCU1 andirinotecan (with or without 5-FC) resulted in significant inhibition oftumor growth compared with the other groups.

Combination VVTK-I4L-/FCU1 and Oxaliplatin

The therapeutic effects of VVTK-I4L-/FCU1 treatment in combination withoxaliplatin were evaluated in vivo on colorectal cancer LoVo cell linein the presence and absence of 5FC prodrug. 5FU was also tested in theseconditions.

More specifically, nude mice (n=11 mice/group) were injectedsubcutaneously with 5×106 LoVo cells. When the tumors had 100-200 mm3,VVTK-I4L-/FCU1 was injected intravenously at 1×107 Pfu on day 21 posttumor implantation. Oxaliplatin was administered intraperitoneally at2.5 mg/kg/day on days 24, 27, 31, 34, 38, 41. Starting on day 28 posttumor implantation, 5-FC was given by oral gavage at 100 mg/kg twice aday for 3 weeks. Starting on day 23 post tumor implantation, 5-FU wasgiven intraperitoneally at 20 mg/kg/day for 3 weeks. Tumor size wasmeasured using calipers. Tumor volume was calculated in mm3 using theformula (π/6) (length×width2). Mice were killed when tumor size exceeded4000 mm3 in volume. Mann-Whitney U-tests were used to determine tumorvolume differences between the groups. A P-value <0.05 was consideredsignificant.

Tumor volume of human colorectal LoVo implanted tumors were measuredregularly (every 4-6 days) after systemic injection ofVVTK-I4L-/FCU1+/−5-FC and oxaliplatin over a period of 52 days posttumor implantation days. Table 7 provides the mean of tumor volumes inmm3 measured in the various mice groups at 19, 25, 32, 46, 49 and 52days after implantation. “oxa” represents oxaliplatin and “VV”VVTK-I4L-/FCU1.

TABLE 7 Group D19 D25 D32 D46 D49 D52 Control 167 379 746 1849 2077 2558oxa 172 283 529 1313 1499 1768 5-FC 169 341 592 1511 1786 1987 oxa + 5FC176 349 682 1476 1899 1828 5-FU 169 293 508 1362 1759 1558 Oxa + 179 309517 1141 1323 1558 5FU VV 175 315 579 1554 1830 1724 VV + 5FC 172 316573 790 836 974 VV + oxa 172 355 555 1024 1089 1215 VV + oxa + 165 328559 657 623 760 5FC

In LoVo model, in terms of tumor growth, treatment with oxaliplatinalone, 5-FC alone, oxaliplatin+5-FC, 5-FU alone, oxaliplatin+5-FU orVVTK-I4L-/FCU1 alone provided a slight control of tumor growth comparedwith control (untreated) mice. VVTK-I4L-/FCU1+ oxaliplatin orVVTK-I4L-/FCU1+5-FC resulted in significant tumor growth controlcompared with no treatment. The greatest benefit in terms of tumorgrowth control was seen with the combinationVVTK-I4L-/FCU1+5-FC+oxaliplatin. Treatment with this combinationresulted in significant inhibition of tumor growth compared with notreatment, oxaliplatin alone, 5-FC alone, oxaliplatin+5-FC,VVTK-I4L-/FCU1 alone, VVTK-I4L-/FCU1+oxaliplatin or VVTK-I4L-/FCU1+5-FC.Moreover the treatment with the combinationVVTK-I4L-/FCU1+5-FC+oxaliplatin resulted in significantly antitumoreffect compared with the chemotherapeutic drug 5-FU alone or incombination with oxaliplatin (5-FU was given intraperitoneally at themaximum tolerated concentrations).

In conclusion, treatment with the combination of VVTK-I4L-/FCU1 andoxaliplatin notably in presence of 5-FC proved to provide an enhancedantitumor effect as compared to each of VVTK-I4L-/FCU1 and oxaliplatinas well as to the standard antitumor drug 5FU.

Statistical Analysis.

Statistical analyses were performed using the nonparametric Mann-WhitneyUtest and STATISTICA 7.1 software (StatSoft, Inc.). A P<0.05 wasconsidered to be statistically significant.

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The invention claimed is:
 1. A method for treating cancer, tumors anddiseases which result from unwanted cell proliferation comprisingadministering to a host organism or cell which is in need an oncolyticOrthopox poxvirus comprising a defective I4L and/or a defective F4Lgene, and a defective J2R gene, or a composition comprising saidpoxvirus, with the proviso that said poxvirus is not NYVAC, andadministering to said host organism or cell a topoisomerase I inhibitorwhich is irinotecan.
 2. The method as defined by claim 1 wherein saidpoxvirus or composition is administered via the systemic route.
 3. Themethod as defined by claim 1 wherein said poxvirus further comprises asuicide gene.
 4. The method as defined by claim 3 wherein said suicidegene encodes a polypeptide comprising an amino acid sequence having atleast 70% identity to that of SEQ ID NO: 1 or SEQ ID NO:
 3. 5. Themethod as defined by claim 4 further comprising an additional step inwhich a pharmaceutically acceptable quantity of a prodrug isadministered to said host organism or cell.
 6. The method as defined byclaim 5 wherein said prodrug is 5 fluorocytosine.
 7. The method asdefined by claim 5 wherein the administration of said prodrug takesplace at least 3 days after the administration of said poxvirus orcomposition.
 8. A method for treating cancer, tumors and diseases whichresult from unwanted cell proliferation comprising administering to ahost organism or cell which is in need an oncolytic Orthopox poxviruscomprising a defective 14L and/or a defective F4L gene and a defectiveJ2R gene or a composition comprising said poxvirus with the proviso thatsaid poxvirus is not NYVAC and further comprising administering to saidhost organism or cell an antimitotic drug which is oxaliplatin.
 9. Themethod as defined by claim 8 wherein said poxvirus or composition isadministered via the systemic route.
 10. The method as defined by claim8 wherein said poxvirus further comprises a suicide gene.
 11. The methodas defined by claim 10 wherein said suicide gene encodes a polypeptidecomprising an amino acid sequence having at least 70% identity to thatof SEQ ID NO: 1 or SEQ ID NO:
 3. 12. The method as defined by claim 11further comprising an additional step in which a pharmaceuticallyacceptable quantity of a prodrug is administered to said host organismor cell.
 13. The method as defined by claim 12 wherein said prodrug is 5fluorocytosine.
 14. The method as defined by claim 12 wherein theadministration of said prodrug takes place at least 3 days after theadministration of said poxvirus or composition.